Balance beam



Dec. 3, 1963 L. B. MAcuRDY BALANCE BEAM Filed March 1, 1962 R www@ m WJ s) WM Nh. `,f/ V11|||||||I1|MINW l0 VJ @n H0. w QW QW QW Om. `N QW WW www.

im N` 44 @am Afro/MEV (ILM 3 I qQI-AGENT United States Patent 3,112,808 i BALANCE BEAM Lloyd E. Macurdy, Silver Spring, Md., assigner to the United States of America as represented by the Secretary of Commerce Filed Mar. 1, 1962, Ser. No. 176,835 3 Claims. (Cl. 177-261) This invention relates to balance beams, and more particularly relates to a balance beam incorporating improved mountings for the knives.

ln the construction of a balance beam for use in a precision balance, a center knife and either one end knife (in the case of a single pan balance) or a pair of end knives (in the case of an equal arm balance) must be mounted thereon such that (1) the edge of each end f lknife is parallel with respect to the edge of the center and holders, and consequently are complex, heavy, andV costly. Y

In accordance with the present invention, a balance beam is provided with a ltransverse channel for each knife, The .bottom of the channel forV the center knife is made planar with the plane thereof parallel to theV desired horizontal reference plane taken through the edge of the center knife. The center knife is mounted in such channel with its base on the planar bottom of the channel and is clamped therein by means which permit the knife to be shifted and/or rotated with respect to the planar bottom. Since the edge of the center knife is parallel to the base, the edgeremains in the horizontal reference plane as the yknife is shifted and rotated on its planar seat.

The bottom of the channel for the end knife is also made planar, but the plane ofthis planar seat is inclined from Ithe horizont-al reference plane, as measured along the length of the beam. The end knife is also clamped by means that permit the knife to be shifted androtated with respect to the seat. Since the seat is inclined, rotation of the knife thereon enables either end of the knife to be raised or lowered so as to position the edge thereof parallel to or within the horizontal reference plane. Shifting ofthe end knife on such inclined seat permits the edge of the knife to be positioned at the desired distance kfrom the horizontal reference plane containing the edge of the center knife. After the end knife is so positioned,

vide improved means for accurately mounting knives on a balance beam.

It is another object to mount knives on a beam by means having seats for knives in which at least one of the seats is inclined from the horizontal reference plane that in cludes the center knife edge.

Other objects and features of ythe invention Wil-l become apparent to those skilled in the art as the disclosure is made in the following detailed description of a preferred ICC embodiment of the drawing as illustrated in the yaccompanying set of drawings, in which:

FlG. 1 is a fron-t elevation of the balance beam embodying the present invention;

FIG. 2 is a cross section view taken along the line 2 2 of FIG. 1, looking in the direction of the arrows.

The exemplary embodiment of the invention shown in FIG. l comprises a beam 1d' provided at one end with acounter-weight 11, whereby the beam is suitable for use in a single pan balance. A .transverse channel 12 is formed in thecentral underside of the beam anda transverse channel 14 is formed in the topside of the beam at the end opposite counterweight 11'.

The bottom surfacesld, 13 of the ch-annels 12, 14 are planar and thus are seats that receive the bases 24, 314 of the center and end knives 2li', 30 respectively. The upper sides l19 of the channels 12, 14 slope outward, thereby pro viding Vashaped spaces'in conjunction with the tapered sides 21, 31 of the knives 20, 30. The V-shaped spaces receive semicylindrical wedges 49, which serve to adjustably clamp knives 2), 30 in place.

It kwill readilybe appreciated that a channel side V19 in conjunction with a knife side (21', 31) defines two intersecting planes, the line of intersection of which varies as the distance between 4the knife and channel side is varied. For example, as the distance between the knife and channel side increases, the line of intersection of the two planes is lowered and shifted away from the channel side 19. In addition, if one end of the knife is moved farther from the channel side than the other end is moved, the line of intersection tilt-s lower near the knife end that was moved farther. Thus, shifting yand rotating the knives 2li, 30 on their seats causes the line of intersection of the planes defined by the V-shaped spaces between the knife sides 21, 31 andthe channel sides 19 to vary.

It will also be readily appreciated that the cylindrical surfaces of the wedges lil tangentially cont-act the planes defined by the V-shaped spaces, with the axis of the cylinder parallel to the line of intersection of the planes. Consequently, it is clear that the two lwedges 40 associated with a knife (2li, 30) can retain the knife against the seat (16, 1S) in any position associated with the shift and/ or rotation of the knife relative to the seat.

To tighten the wedges 49, bolts Sil are provided as shown in FIG. 2. The bolts Si) pass through holes provided in the wedges 'and further pass through holes drilled into the beam 10, so as to thread into swivel nuts 52, disposed iu transverse bores provided in beam 10. The swivel nuts 52 permit the cylindrical axes of the sem-icylindrica-l wedges 4t) to align parallel with the line of intersection of the intersecting planes defined by the channel side 19 and knife side (21, 31) as bolts S2 are tightened.

in practice, the bolts 5d in conjunction with wedges 4t) not only clamp the knives 20, 30in position, but serve as means for micromatically positioning the knives, inasmuch as the tightening of a bolt 5t) causes that end of the wedge 4t? therebeneath Ito penetrate into the V-shaped space between the sloping channel side 19 and sloping knife side (21, 31), thereby tending to move the adjacent end of the knife away from the channel side 19. It is of course necessary that one or bothv of the bolts 50 associated with the wedge 40 disposed on the opposite side of the knife be loosened so that the knife may shift.

ln accordance with ythe present invention, the plane of seat lkassociated with center knife i26* is made parallel to thehorizontal reference plane that includes line P-`-P and extends normal to the plane of FIG. 1. The center knife Ztl is formed so that the edge 22 is parallel to the ybase 24. Consequently, the knife 2G may be shifted and rotated on the seat 16, and the edge ZZ will rernaintin lthe horizontal reference plane represented by line PwP.

The seat 18 provided for the end knife 3? is also planar,

but the plane thereof is slightly inclined from the horizontal reference plane with the line of intersection of said planes 'being substantially normal to the vertical plane of symmetry of beam 1t). The angle of inclination Vat preferably is in the order of a few degrees.- Since the seat 1S is inclined, rotation of the end knife 3@ thereon by means of the wedges 40 as described above permits the ends of edge 32 of the knife Sil to be brought into position parallel -with the horizontal reference plane that includes line P-P. The knife 3@ may then be shifted up or down the inclined seat 1S until the edge 32 is at the desired distance from the horizontal reference plane. After the end knife 3) is adjusted in the manner just described, the center knife 20 is rotated if necessary until its edge 22 is parallel with the edge 32 of the end knife 30. 'Ilhen the center knife is shifted so as to adjust the distance bet-Ween its edge 2.2 and the edge 32 of end knife 30, whereby the knives are in completed position.

-In FIG. l, the center seat 16 is formed such that its plane is horizontal, while the plane of end seat 18 is inclined from the horizontal as measured along the length of beam 10. It will be appreciated `that the relationship could be reversed with end seat 1S being horizontal and center seat 1.6 inclined. It is also evident that the inclined seat ll, shown as sloping downward from right to left, could slope downward in the reverse direction from left to right, as measured along the length of beam lil.

'In the embodiment shown in FIGS. 1 and 2, the beam T10-is for use ina single pan balance and is provided at one end with a counter'weight 11. Consequently, the beam 10 has only one end knife St). In the case of a beam for `use in a two-pnn (equal arm) balance, the lbeam would be provided with two end knives. In such a beam, the presentinvention may be practiced in several ways, Any one of the three seats for the three knives could be inclined, while the other .two are made horizontal. Alternatively, the seats for the end knives may be both inclined, and the center seat may be horizontal. -In the latter embodiment, the end knives are shifted on their seats to secure the desired distance between their edges and the horizontal reference plane passing through the edge of the center knife. The center knife is then shifted on its horizontal seat to achieve equality of the arm lengths.

While the'knives 20, 30 have been illustrated as adjust- 4 ably clamped to their respective seats by means of Wedges 40, which .are preferred because they provide a means for accurately positioning the knives in addition to clamping same, it will be appreciated that alternative adjustable clamping means tmay be employed Within the scope of the invention. For example, each of the knives could be clamped `to the beam by providing a threaded 4hole in the base of the knife, so as to receive a bolt disposed in an oversize hole drilled through the beam in the center of the seat, whereby the knife may be shifted and/or rotated as permitted bythe oversize hole surrounding the bolt. Tightening of the bolt into the threaded base of the knife would of course draw the knife into snug engagement with the seat and thereby lock the position of the knife.

The invention has been shown and described in a single preferred form and by way of example, and obviously many variations and modifications may lbe m-ade therein Without departing from the spirit of the invention. It is to be understood, therefore, that the invention .is not to be limited to any specific form or embodiment except insofar as such limitations .are specified in the appendent claims.

What is claimed is:

1. In a balance, the combination of a horizontal beam having a planar center seat `and at least one planar end seat, the plane of one of said seats being horizontal, and the plane of the other of said seats being inclined from the horizontal as measured along the length of said beam, at least two movable knives, and means for adjustably clamp ing said knives to'said seats.

2. The combination set forth in claim y1, wherein said seats are the bottoms of Itransverse channels in said beam.

3. The combination set forth in claim 2, wherein said channels have sides which slope outwardly, said clamping -rneans comprising semicylindrical wedges disposed between said ychannel sides and the adjacent sides of said knives, said wedges being vertically and laterally adjustable, whereby said knives may be shifted and rotated Iwith respect to said seats.

References Cited in the tile of this patent UNITED STATES PATENTS 638,990 Replogle Dec. l2, 1899 1,065,844 Sartorius lune 24, 1913 2,319,322 Hefel May 18, 1943 2,729,438 Wasco Jan. 3, 1956 

1. IN A BALANCE, THE COMBINATION OF A HORIZONTAL BEAM HAVING A PLANAR CENTER SEAT AND AT LEAST ONE PLANAR END SEAT, THE PLANE OF ONE OF SAID SEATS BEING HORIZONTAL, AND THE PLANE OF THE OTHER OF SAID SEATS BEING INCLINED FROM THE HORIZONTAL AS MEASURED ALONG THE LENGTH OF SAID BEAM, AT LEAST TWO MOVABLE KNIVES, AND MEANS FOR ADJUSTABLY CLAMPING SAID KNIVES TO SAID SEATS. 